Tanning with a condensation product of acrolein and formaldehyde



United States Patent 3 346 324 TANNING WITH A CO NDIENSATION PRODUCT 0F ACROLEIN AND FORMALDEHYDE Martin L. Fein and Edward M. Filachione, Philadelphia,

Pa., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed June 24, 1964, Ser. No. 377,776 4 Claims. (Cl. 8-94.26)

ABSTRACT OF THE DISCLOSURE Applicants tan hides with the alkaline condensates of acrolein and formaldehyde which forms a mixture of compounds having the following formula CH2OH HO --CH2-C- OHQOH CHO a The tanning is done under acid conditions and in combination with chrome tanning agents.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the World for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the tanning of animal hides and skins by impregnating them with a novel water-soluble condensation product of acrolein and formaldehyde, and to the leather thus produced.

Although the individual compounds formaldehyde and acrolein are classed as tanning agents, there are objectionable features to their use for this purpose. These aldehydes are diflicult to handle because of their obnoxious and irritating properties. In fact, acrolein is an extremely hazardous material to handle. Formaldehyde is advantageous only because it produces White leather. In other respects the leather produced with this aldehyde is not desirable, it being well-known that formaldehyde tannage results in a flat leather that is diflicult to process into finished leather.

An object of this invention is to produce a white leather wtih pleasing characteristics. A further object is to impart improved properties to leather. Another object is to develop a rapid process for tanning animal hides and skins. Other objects and a fuller understanding of the invention may be had by referring to the following description and claims.

We have found that a condensation product of acrolein and formaldehyde, obtained under alkaline conditions, possesses unexpected tanning ability. This product, known as X-Z Chemical Reactor and X2S Chemical Reactor was made available by Dan River Mills and is represented by the formula wherein n is an integer from 1 to 5, inclusive. This condensation product is not a single compound but a mixture of various components represented by the formula. In this invention, when we use the term X2S Chemical Reactor, or more simply, X-2-S, we mean a condensation product of acrolein and formaldehyde as specified above.

Although a hydroxy aldehyde, this condensation product of acrolein and formaldehyde was found to be an effective tanning agent. The prior art teaches that hydroxy 3,346,324 Patented Oct. 10, 1967 aldehydes, of which sugars such as arabinose and glucose are well-known examples, are lacking in tanning ability. Yet the hydroxy aldehyde employed in the present process gives a white, soft, mellow leather.

In the process of our invention animal hides or skins are treated with an aqueous solution of a condensation product of acrolein and formaldehyde until tanned. The aqueous solution may be either slightly acidic (above pH 4.0), neutral, or alkaline. To obtain the best results with this condensation product, however, we prefer to carry out the tanning in mildly alkaline solution. The tanned hides or skins may then be processed into finished leather by the normal processes applied to chrome or vegetabletanned hides or skins.

The hides and skins tanned with this condensation product alone produced a soft, white, mellow and acceptable leather. However, this new tanning agent may also be used in combination with conventional tanning agents such as vegetable tannins, chrome, zirconium, aluminum, etc. In combination with conventional tanning agents, the process can be carried out consecutively or simultaneously. For example with chrome, the skins may be tanned first with the condensation product of acrolein and formaldehyde, then retanned with chrome; or the reverse sequence may be used. Equally satisfactorily the condensation product and chrome may be used simultaneously in the same tanning bath.

The following examples illustrate the process of the invention. The scope of the invention is not limited to the exact manner in which these examples were carried out. For instance, pickled skins can be added to an aqueous solution at pH above neutrality containing a condensation product of acrolein and formaldehyde. Equally well, the pickled skins can be added to an aqueous solution of the condensation product of acrolein and formaldehyde at a pH in the acidic range and then the pH can be raised to the level desired for tanning.

In the following examples the calfskin specimens and treatment solutions were in 4 oz. screw-capped bottles which were placed on rollers turning at approximately 36 r.p.m. The rollers turned continuously during the day and intermittenly from 5 pm. to 7 am. (45 minutes onl5 minutes off).

Example 1 Two strips each of iso-electr-ic and dehydrated cowhide and calfskin (1" x 3") were treated with a solution comprising 10 grams X-Z-S Chemical Reactor (a water soluble condensation product of acrolein and formaldehyde available from Dan River Mills) and grams water. After 3 days of reaction at pH 5.0 (with no salts or buffers), the shrink temperature (T for the calfskin was 87 C., for the cowhide, 88 C. The test pieces, when air dried, were leather-like, white and flexible.

Example 2 About grams of X2S Chemical Reactor solution was treated with steam for 27 hours. At the end of this time the residue, which contained the soluble acrolein formaldehyde condensation product amounted to about 300 grams and hence was one-third the concentration of the original solution.

Five strips (1" x 3") of wet depickled calfskin, of total weight 22 grams, were treated with 30 ml. of the above refined solution of X2$ Chemical Reactor diluted with an additional 70 ml. of water, with no additional salts or buffers. The pH during the 2-day treatment time was 5.0 to 4.9. The shrink temperature after 1 and 2 days of treatment was 79 C. for both. The product was fibrous and leather-like, but quite stiff, in each case.

3 Example 3 Five strips (1" x 3") of wet depickled calfskin of total weight 21 grams were treated with a solution comprising 30 ml. X2-S Chemical Reactor (refined as described in Example 2), 70 ml. water, and 10 grams Na' SO The pH during a 2-day treatment was 5.25.3. The shrink temperature after 1 day was 79 C., after 2 days, 80 C. The product was white, fibrous and leather-like after the one day treatment; The product of the 2-day treatment was similar except that it was much more flexible and considered very good.

Example 4 7 Four strips (1" x 3") depickled calfskin of total weight 20 grams were treated with a solution comprising 30 m1. XZ-S Chemical Reactor (as described in Example 2), 70 ml. water, 10 grams Na SO and 2.1 grams NaHCO The pH during a 2-day treatment period was 7.7 to 8.2. The shrink temperature after 2 hours was 81 C., and after 6 hours the T was 8485 C. and showed no further increase even after 2 days. The leather product at 6 hours and thereafter was white, fibrous and good.

Example 5 Example 6 Four strips (1" x 3") depickled calfskin of total weight 22 grams were treated with a solution comprising 30 mil. XZ-S Chemical Reactor (as described in Example 2), 70 ml. water, grams Na SO and 1 gram MgO. The pH during a 2-day treatment was 10.3-10.6. The shrink temperature at 2 hours was 73 C., at 6 hours 83C., at one and two days 87 C. All specimens, from 6 hour to 2 day treatment, were white, fibrous and leather-like. The 6 hour and 1 day specimens were very good.

We claim:

1. A process for tanning hides and skins comprising impregnating said hides and skins under acid conditions with a solution of a Water-soluble condensation product, produced by condensation between acrolein and ormaldehyde under alkaline conditions, until the hides and skins are tanned.

2. A process for tanning hides and skins comprising impregnating said hides and skins under acid conditions with an aqueous solution containing a mixture of compounds of the formula wherein n is an integer of 1 to 5, inclusive, until the hides and skins are tanned.

3. A process for tanning hides and skins comprising impregnating said hides and skins under acid conditions with an aqueous solution containing a mixture of compounds of the formula wherein n is an integer of 1 to 5, inclusive, and a mineral tanning agent until the hides and skins are tanned.

4. The process of claim 3 in which the mineral tanning agent is a chromium compound.

References Cited UNITED STATES PATENTS 1/1956 Gag'arine 8-116 X FOREIGN PATENTS 1,294,398 4/1962 France.

I 2,872 7 1898 Great Britain.

DONALD LEVY, Primary Examiner. 

1. A PROCESS FOR TANNING HIDES AND SKINS COMPRISING IMPREGNATING SAID HIDES AND SKINS UNDER ACID CONDITIONS WITH A SOLUTION OF A WATER-SOLUBLE CONDENSATION PRODUCT, PRODUCED BY CONDENSATION BETWEEN ACROLEIN AND FORMALDEHYDE UNDER ALKALINE CONDITIONS, UNTIL THE HIDES AND SKINS ARE TANNED. 